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Showing 1561–1580 of 2058 publications.
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Stadler, Nadina; Lindner, Robyn A.; Davies, Michael J.Objective-The involvement of transition metals in atherosclerosis is controversial. Some epidemiological studies have reported a relationship between iron (Fe) and cardiovascular disease, whereas others have not. Experimental studies have reported elevated levels of iron and copper (Cu) in diseased human arteries but have often used methods that release metal ions from proteins. Methods and Results-In this study, we have used the minimally invasive technique of electron paramagnetic resonance (EPR) spectroscopy and inductively coupled plasma mass spectroscopy (ICPMS) to quantify iron and copper in ex vivo healthy human arteries and carotid lesions. The EPR spectra detected are characteristic of nonheme Fe(III) complexes. Statistically elevated levels of iron were detected in the intima of lesions compared with healthy controls (0.370 versus 0.022 nmol/mg tissue for EPR, 0.525 versus 0.168 nmol/mg tissue by ICPMS, P<0.05 in each cases). Elevated levels of copper were also detected (7.51 versus 2.01 pmol/mg tissue, lesion versus healthy control, respectively, P<0.05). Iron levels did not correlate with the gender or age of the donor, or tissue protein or calcium levels, but cholesterol levels correlated positively with iron accumulation, as measured by EPR. Conclusions-These data support the hypothesis that iron accumulates in human lesions and may contribute to disease progression.
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Makris, Angela; Thornton, Charlene Eliza; Hennessy, AnnemarieNonsteroidal analgesics are frequently used in obstetrics. We present two cases where nonsteroidal analgesics contributed to significant elevations in blood pressure in postpartum women. We review the literature and consider the pathophysiologic causes for such a phenomenon. 2004 Elsevier Inc. All rights reserved.
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Barter, Philip J.The concentration of high density lipoprotein cholesterol (HDL-C) has been found to be a powerful negative predictor of premature coronary heart disease (CHD) and stroke in human prospective population studies. Evidence of the protective properties of HDLs has also been documented in the elderly and their offspring. HDLs mediate several functions that provide an insight into their potential anti-atherogenic mechanisms. Intervention strategies to prevent CHD have generally focused on lowering low-density lipoprotein cholesterol (LDL-C). However, several lifestyle and pharmacological interventions have the capacity to raise the level of HDL-C. As data accumulate on the protective role of HDLs, there is growing support for interventions that act to raise HDL-C concentrations. 2004 Elsevier Ireland Ltd. All rights reserved.
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Stocker, Roland; O'Halloran, Ruth A.Background: Oxidation of LDL is thought to be important in the development of atherosclerosis. Effective protection against lipoprotein oxidation is achieved by the use of ?-tocopherol plus coantioxidants - ie, compounds that prevent the prooxidant activity of the vitamin. Wines contain a large number of polyphenols, micronutrients that may act as coantioxidants and may enhance the in vivo antioxidant activity of vitamin E. Objective: We examined whether wines and wine-derived fractions are able to act synergistically with vitamin E in vitro and whether dealcoholized red wine (DRW) retards the development of atherosclerosis. Design: Synergy with vitamin E was assessed in vitro by the ability of red and white wines to both attenuate ?-tocopheroxyl radicals and inhibit in vitro oxidation of LDL in the presence of vitamin E. Female, 6-8-wk-old apolipoprotein E gene-deficient mice were fed a normal nonpurified stock diet for 24 wk to assess the effect on atherosclerosis of DRW at a dose equivalent to 200 mL80 kg body wt -1d-1. Results: DRW synergized with vitamin E as effectively as did red and white wine, and phenolic acids accounted for most of this activity. Administration of DRW increased plasma and aortic antioxidants concentrations and the resistance of plasma lipoproteins to ex vivo oxidation. Whereas lipoprotein oxidation in the artery wall was not affected, DRW significantly decreased atherosclerosis in the aortic arch, but not in the root, as assessed by morphometry. Conclusions: DRW contains polyphenolic compounds capable of synergizing with vitamin E, and long-term moderate consumption of DRW can decrease atherosclerosis in apolipoprotein E gene-deficient mice. 2004 American Society for Clinical Nutrition.
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Makris, Angela; Thornton, Charlene Eliza; Hennessy, Annemarie; Rayman, M. P.; Bode, Peter; Redman, Christopher W.G.[No abstract available]
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Davies, Michael J.Singlet oxygen (1O<inf>2</inf>) is believed to be generated in biological systems by a range of endogenous processes (e.g. enzymatic and chemical reactions) and exogenous stimuli (e.g. UV or visible light in the presence of a sensitiser). Kinetic data is consistent with proteins being a major target for 1O<inf>2</inf>, with damage occurring preferentially at Trp, His, Tyr, Met, and Cys side-chains. Reaction with each of these residues gives rise to further reactive species. In the case of Trp and Tyr, initial poorly characterised endoperoxides are believed to undergo ring-opening reactions to give hydroperoxides, which can be reduced to the corresponding alcohols; other products arising from radical intermediates can also be generated, particularly in the presence of UV light and metal ions. With His side-chains, poorly characterised peroxides are also formed. Reaction with Met and Cys has been proposed to occur via zwitterionic peroxy intermediates. Peroxides are also generated on isolated proteins, and protein within intact cells, via 1O<inf>2</inf>-mediated reactions. The peroxides formed on Trp, Tyr, and His peptides, as well as on proteins, have been shown to induce damage to other targets, with molecular oxidation of thiol residues an important reaction. This can result in the inactivation of cellular enzymes and the oxidation of other biological targets. Protein cross-linking and aggregation can also be induced by reactive species formed on photo-oxidised proteins, though the nature of the species that participate in such reactions is poorly understood. These secondary reactions, and particularly those involving hydroperoxides, may play a key role in the induction of secondary damage (bystander effects) in systems subject to photo-oxidation. 2004 The Royal Society of Chemistry and Owner Societies.
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Nelson, Margaret; Cooper, Simon; Nakhla, Shirley; Smith, Susan Wallace G.; King, Malcolm Anthony; Ashenden, Michael J.The present study has been undertaken to validate a recently described flow cytometric method for the detection of homologous blood transfusion by elite athletes that utilises a panel of different RBC antibodies to detect mixed RBC populations. Single or mixed RBC suspensions of known phenotype were prepared by the reference laboratory from commercial screening-test kits. These were distributed to the participating laboratories together with buffer, antibody samples and detailed instructions for staining and analysing the samples. Initial technical training identified certain unexpected problems, which were remedied during the course of this study. The final analyses of a series of unknown samples were correctly assessed for evidence of "transfusion" by the four separate operators. The detection and quantitation of mixed RBC populations is not dependent on the type or model of flow cytometer. Training of technical staff not familiar with handling RBCs was found to be necessary before consistent results were obtained. There was agreement between all laboratories as to the presence or absence of mixed RBC populations consistent with a post-transfusion sample.
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Morgan, Philip E.; Dean, Roger T.; Davies, Michael J.Reaction of certain amino acids, peptides, and proteins with singlet oxygen yields substrate-derived peroxides. Recent studies have shown that these species are formed within intact cells and can inactivate key cellular enzymes. This study examines potential mechanisms by which cells might remove or detoxify such peroxides. It is shown that catalase, horseradish peroxidase, and Cu/Zn superoxide dismutase do not react rapidly with these peroxides. Oxymyoglobin and oxyhemoglobin, but not the met (Fe3+) forms of these proteins, react with peptide but not protein, peroxides with oxidation of the heme iron. Glutathione peroxidase, in the presence of reduced glutathione (GSH) rapidly removes peptide, but not protein, peroxides, consistent with substrate size being a key factor. Protein thiols, GSH, other low-molecular-weight thiols, and the seleno-compound ebselen react, in a nonstoichiometric manner, with both peptide and protein peroxides. Cell lysate studies show that thiol consumption and peroxide removal occur in parallel; the stoichiometry of these reactions suggests that thiol groups are the major direct, or indirect, reductants for these species. Ascorbic acid and some derivatives can remove both the parent peroxides and radicals derived from them, whereas methionine and the synthetic phenolic antioxidants Probucol and BHT show little activity. These studies show that cells do not have efficient enzymatic defenses against protein peroxides, with only thiols and ascorbic acid able to remove these materials; the slow removal of these species is consistent with protein peroxides playing a role in cellular dysfunction resulting from oxidative stress. 2003 Elsevier Inc. All rights reserved.
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Rye, Kerry Anne; Barter, Philip J.The preferred extracellular acceptor of cell phospholipids and unesterified cholesterol in the process mediated by the ATP-binding cassette A1 (ABCA1) transporter is a monomolecular, prebeta-migrating, lipid-poor or lipid-free form of apolipoprotein (apo) A-I. This monomolecular form of apoA-I is quite distinct from the prebeta-migrating, discoidal high-density lipoprotein (HDL) that contains two or three molecules of apoA-I per particle and which are present as minor components of the HDL fraction in human plasma. The mechanism of the ABCA1-mediated efflux of phospholipid and cholesterol from cells has been studied extensively. In contrast, much less attention has been given to the origin and subsequent metabolism of the acceptor lipid-free/lipid-poor apoA-I. There is a substantial body of evidence from studies conducted in vitro that a monomolecular, lipid-free/lipid-poor form of apoA-I dissociates from HDL during the remodeling of HDLs by plasma factors such as cholesteryl ester transfer protein, hepatic lipase, and phospholipid transfer protein. The rate at which apoA-I dissociates from HDL is influenced by the phospholipid composition of the particles and by the presence of apoA-II. This review describes current knowledge regarding the formation, metabolism, and regulation of monomolecular, lipid-free/lipid-poor apoA-I in plasma.
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Barter, Philip J.Low high-density lipoprotein (HDL-C) cholesterol is a powerful predictor of risk for coronary heart disease (CHD), and raising HDL-C reduces CHD risk, with available data indicating a 1% decrease in risk with each 1% increase in HDL-C. Both epidemiological and intervention studies have shown that HDL is predictive of risk independent of low-density lipoprotein cholesterol. In treatment trials, both fibrates and statins have been shown to reduce risk in patients with low HDL-C. Statins reduce risk across all HDL-C levels from low to high, whereas fibrates appear to have benefits limited to low HDL-C in the context of the metabolic syndrome. The primary management component of increasing HDL-C is lifestyle intervention focusing on diet, exercise and smoking cessation. Drug options for raising HDL-C include niacin (+10-30%), fibrates (+5-25%) and statins (+3-12%). Niacin is poorly tolerated. Fenofibrate may pose advantages over gemfibrozil among fibrates. Findings in the large-scale Statin Therapies for Elevated Lipid Levels compared Across dose ranges to Rosuvastatin (STELLAR) trial indicate that rosuvastatin has the best HDL-C raising effect among statins. Selection of therapy requires consideration of the individual patient's overall risk profile. 2004 The European Society of Cardiology. Published by Elsevier Ltd. All rights reserved.
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Heather, Alison Kay; McGrath, Kristine C.Y.; Sader, Mark A.; Nakhla, Shirley; Jessup, Wendy K.; Handelsman, David J.; Celermajer, David S.There exists a striking gender difference in atherosclerotic vascular disease. For decades, estrogen was considered atheroprotective; however, an alternative is that androgen exposure in early life may predispose men to earlier atherosclerosis. We recently demonstrated that the potent androgen, dihydrotestosterone (DHT), enhanced the binding of monocytes to the endothelium, a key early event in atherosclerosis, via increased expression of vascular cell adhesion molecule-1 (VCAM-1). We now show that DHT mediates its effects on VCAM-1 expression at the promoter level through a novel androgen receptor (AR)/nuclear factor-?B (NF-?B) mechanism. Human umbilical vein endothelial cells were exposed to 4-400 nM DHT. DHT increased VCAM-1 mRNA in a dose- and time-dependent manner. The DHT effect could be blocked by the AR antagonist, hydroxyflutamide. DHT increased VCAM-1 promoter activity via NF-?B activation without affecting VCAM-1 mRNA stability. Using 5? deletion analysis, it was determined that the NF-?B sites within the VCAM-1 promoter region were responsible for the DHT-mediated increase in VCAM-1 expression; however, coimmunoprecipitation studies suggested there is no direct interaction between AR and NF-?B. Instead, DHT treatment decreased the level of the NF-?B inhibitory protein. DHT did not affect VCAM-1 protein expression and monocyte adhesion when female endothelial cells were tested. AR expression was higher in male, relative to female, endothelial cells, associated with increased VCAM-1 levels. These findings highlight a novel AR/NF-?B mediated mechanism for VCAM-1 expression and monocyte adhesion operating in male endothelial cells that may represent an important unrecognized mechanism for the male predisposition to atherosclerosis.
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Woodman, R. J.; Celermajer, David S.; Thompson, Peter Lindsay; Hung, Joseph C.Folic acid supplementation lowers total plasma homocysteine (tHcy) and improves endothelial function in individuals with coronary artery disease (CAD) and in those with additional CAD risk factors. In the present study, we assessed whether endothelial function is impaired in healthy subjects with hyperhomocysteinaemia but without other CAD risk factors and whether folic acid supplementation improves endothelial function in these subjects. Flow-mediated dilatation (FMD) of the brachial artery was performed on 26 healthy subjects, age 49 2 years (mean S.E.M.), with high tHcy (15.6 1.5 ?mol/l) and 16 healthy age-matched subjects with low tHcy (7.9 0.6 ?mol/l; P < 0.001). Subjects with high tHcy were then randomized to receive 5 mg/ day of folic acid or placebo for 8 weeks in a double-blind cross-over trial with a 4-week washout. FMD was not associated with tHcy and was not different between high and low tHcy groups (7.0 0.6% compared with 6.6 1.2%, P = 0.76). Treatment with folic acid decreased tHcy by 34% in hyperhomocysteinaemic subjects (P = 0.02 compared with placebo), but had no effect on FMD (+ 0.5 0.6% compared with -0.7 0.5%; P = 0.17 compared with placebo). In healthy subjects with hyperhomocysteinaemia, but without additional cardiovascular risk, endothelial function is unimpaired and folic acid supplementation has no additional effect.
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Schuster, Herbert M.; Barter, Philip J.; Stender, Steen; Cheung, Raphael C.; Bonnet, Jacques E.; Morrell, Jonathan M.; Watkins, Claire; Kallend, David G.; Raza, AliBackground In a multinational trial (4522IL/0081), we assessed the effects of switching to low doses of rosuvastatin from commonly used doses of atorvastatin, simvastatin, and pravastatin on low-density lipoprotein cholesterol (LDL-C) goal achievement in high-risk patients. Methods Hypercholesterolemic patients (n = 3140) with coronary heart disease, atherosclerosis, or type 2 diabetes were randomized to open-label rosuvastatin 10 mg, atorvastatin 10 or 20 mg, simvastatin 20 mg, or pravastatin 40 mg for 8 weeks. Patients either remained on these treatments for another 8 weeks or switched treatments from atorvastatin 10 mg, simvastatin 20 mg, and pravastatin 40 mg to rosuvastatin 10 mg or from atorvastatin 20 mg to rosuvastatin 10 or 20 mg. The primary efficacy measure was the proportion of patients reaching the Joint European Societies' LDL-C goal (<116 mg/dL) at week 16. For measures of cholesterol goal achievement, treatment arms were compared using logistic-regression analysis. Results Significant improvement in LDL-C goal achievement was found for patients who switched to rosuvastatin 10 mg, compared with patients who remained on atorvastatin 10 mg (86% vs 80%, P < .05), simvastatin 20 mg (86% vs 72%, P < .0001), and pravastatin 40 mg (88% vs 66%, P < .0001), and between patients switched to rosuvastatin 20 mg and those who remained on atorvastatin 20 mg (90% vs 84%, P < .01). Similar results were found for achievement of the European combined LDL-C and total cholesterol goals and National Cholesterol Education Program Adult Treatment Panel III LDL-C goals. All statins were well tolerated over 16 weeks. Conclusions We demonstrated that switching to a more efficacious statin is an effective strategy to improve lipid goal achievement in patients requiring lipid-lowering therapy.
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Sunde, Margaret; McGrath, Kristine C.Y.; Young, Lei; Matthews, Jacqueline M.; Chua, Elizabeth L.; Mackay, Joel P.; Heather, Alison KayA novel gene, thyroid cancer 1 (TC-1), was found recently to be overexpressed in thyroid cancer. TC-1 shows no homology to any of the known thyroid cancer-associated genes. We have produced stable transformants of normal thyroid cells that express the TC-1 gene, and these cells show increased proliferation rates and anchorage-independent growth in soft agar. Apoptosis rates also are decreased in the transformed cells. We also have expressed recombinant TC-1 protein and have undertaken a structural and functional characterization of the protein. The protein is monomeric and predominantly unstructured under conditions of physiologic salt and pH. This places it in the category of natively disordered proteins, a rapidly expanding group of proteins, many members of which play critical roles in cell regulation processes. We show that the protein can be phosphorylated by cyclic AMP-dependent protein kinase and protein kinase C, and the activity of both of these kinases is up-regulated when cells are stably transfected with TC-1. These results suggest that overexpression of TC-1 may be important in thyroid carcinogenesis.
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Pattison, David I.; Davies, Michael J.Hypohalous acids (HOX, X = Cl, Br) are produced by activated neutrophils, monocytes, eosinophils, and possibly macrophages. These oxidants react readily with biological molecules, with amino acids and proteins being major targets. Elevated levels of halogenated Tyr residues have been detected in proteins isolated from patients with atherosclerosis, asthma, and cystic fibrosis, implicating the production of HOX in these diseases. The quantitative significance of these findings requires knowledge of the kinetics of reaction of HOX with protein targets, and such data have not been previously available for HOBr. In this study, rate constants for reaction of HOBr with protein components have been determined. The second-order rate constants (22 C, pH 7.4) for reaction with protein sites vary by 8 orders of magnitude and decrease in the order Cys > Trp ? Met ? His ? ?-amino > disulfide > Lys ? Tyr ? Arg > backbone amides > Gln/Asn. For most residues HOBr reacts 30-100 fold faster than HOCl, though Cys and Met residues are ?10-fold less reactive, and ring halogenation of Tyr is ?5000-fold faster. Thus, Tyr residues are more, and Cys and Met much less, important targets for HOBr than HOCl. Kinetic models have been developed to predict the targets of HOX attack on proteins and free amino acids. Overall, these results shed light on the mechanisms of cell damage induced by HOX and indicate, for example, that the 3-chloro-Tyr:3-bromo-Tyr ratio does not reflect the relative roles of HOCl and HOBr in disease processes.
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Headlam, Henrietta A.; Davies, Michael J.Exposure of proteins to radicals in the presence of O<inf>2</inf> gives both side-chain oxidation and backbone fragmentation. These processes can be interrelated, with initial side-chain oxidation giving rise to backbone damage via transfer reactions. We have shown previously that alkoxyl radicals formed on the C-3 carbons of Ala, Val, Leu, and Asp residues undergo ?-scission to give backbone ?-carbon radicals, with the release of the side- chain as a carbonyl compound. We now show that this is a general mechanism that occurs with a wide range of oxidants. The quantitative significance of this process depends on the extent of oxidation at C-3 compared with other sites. HO , generated by ? radiolysis, gave the highest total carbonyl yield, with protein-bound carbonyls predominating over released. In contrast, metal ion/H<inf>2</inf>O<inf>2</inf> systems, gave more released than bound carbonyls, with this ratio modulated by EDTA. This is ascribed to metal ion - protein interactions affecting the sites of initial oxidation. Hypochlorous acid gave low concentrations of released carbonyls, but high yields of protein-bound material. The peroxyl radical generator 2,2?-azobis(2- amidinopropane) hydrochloride, and a peroxynitrite generator, 3-morpholinosydnonimine hydrochloride, gave lower overall carbonyl yields, with released carbonyls predominating over protein-bound species similar to that observed with metal ion/H<inf>2</inf>O<inf>2</inf> systems. 2004 Elsevier Inc. All rights reserved.
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Davies, Michael J.; Hawkins, Clare L.Electron paramagnetic resonance (EPR) spin trapping was originally developed to aid the detection of low-molecular-mass radicals formed in chemical systems. It has subsequently found widespread use in biology and medicine for the direct detection of radical species formed during oxidative stress and via enzymatic reactions. Over the last 15 years this technique has also found increasing use in detecting and identifying radicals formed on biological macromolecules as a result of either radical reactions or enzymatic processes. Though the EPR signals that result from the trapping of large, slowly tumbling radicals are often broad and relatively poor in distinctive features, a number of techniques have been developed that allow a wealth of information to be obtained about the nature, site, and reactions of such radicals. This article summarizes recent developments in this area and reviews selected examples of radical formation on proteins. 2004 Elsevier Inc. All rights reserved.
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Heather, Alison Kay; McGrath, Kristine C.Y.; Kazlauskas, Rymantas; Handelsman, David J.Tetrahydrogestrinone (THG) was recently identified as a novel steroid used illicitly to improve athletic performance. Although its structure is closely related to gestrinone, a 19-nor progestin, and resembles that of trenbolone, THG was never marketed, so information on its hormonal properties is not known. In this study, we demonstrate that THG is a highly potent androgen and progestin in a yeast-based in vitro bio-assay system expressing human androgen and progesterone receptors. It has no estrogenic activity and no antagonism for any of the three steroid receptor classes.
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Nicholls, Stephen J.; Lundman, PiaLow-density lipoprotein cholesterol has a well-established role in atherogenesis and the development of coronary heart disease. However, despite effective lowering of low-density lipoprotein cholesterol, many patients continue to have cardiovascular events. It has subsequently emerged that several additional dyslipidemic states promote atherogenesis. In particular, the atherogenic lipoprotein phenotype comprising an elevation of triglycerides and triglyceride-rich lipoproteins; decreased concentrations of high-density lipoprotein cholesterol; and increased small, dense low-density lipoprotein cholesterol, in addition to impaired postprandial lipemia, have been demonstrated to have profound effects on the arterial wall. As such, these factors have become important targets in the development of effective strategies to prevent atherosclerotic cardiovascular disease.
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Richardson, Des RaymondThe success of DFO at markedly inhibiting the growth of aggressive tumors such as neuroblastoma and leukemia justifies interest in the development of chelators as anti-neoplastic agents. This is emphasized by the fact that DFO has suboptimal properties, namely poor membrane permeability and a very short serum half-life. More recently, the thiosemicarbazone chelator, Triapine, has entered a phase I clinical trial again confirming the potential of these compounds. Further studies examining the effects of chelators on neoplastic cells will not only be valuable in terms of identifing novel anti-cancer agents, but will also provide new information on the role of Fe in cell cycle control.
